Wiring device



y 1962 I c. M. SMITH 3,036,285

WIRING DEVICE Filed Nov. 29, 1957 49 g 43 r 39 ////A v 3 I r/l Fig.3. I5H Fig.5.

INVENTOR 3| 3| Clarence M. Smnrh ATTORNEY Sits ite

This invention relates to electric wiring devices and more particularlyto improved grounding contacts for such wiring devices.

One object of the invention is to provide a receptacle having animproved grounding contact adapted to cooperate with a male plug havinga grounding prong for grounding appliances and the like.

Another object of the invention is to provide an improved plug and wallreceptacle therefor which when receiving the plug makes a ground contactin advance of any electrical connection and which breaks the groundcontact after the electrical connections have been broken.

Another object of the invention is to provide a plug and plug receptaclewhich is of simple and durable construction and is inexpensive tomanufacture.

The invention both as to structure and operation, together withadditional objects and advantages thereof, will be best understood fromthe following detailed description thereof, when read in conjunctionwith the accompanying drawings.

In said drawings:

FIGURE 1 is a top plan view of a receptacle embodying the principles ofthe invention;

FIG. 2 is a plan view of the receptacle with the cover removed;

' FIG. 3. is a longitudinal sectional view taken on line III-I'll ofFIG. 1 and looking in the direction indicated 'by the arrows;

atcnt G FIG. 4 is a transverse sectional view taken on line IV-IV ofFIG. 1 and looking in the direction of the arrows; and

FIG. 5 is an elevational view showing the plug for use with thereceptacle.

Referring to the drawing, the receptacle comprises a base 11 and a cover13 both of molded insulating material secured together by screws 15which pass through openings in the base '11 and threadedly engage inopenings in the cover 13. A mounting yoke 17 is clamped between the base11 and cover 13, and two oppositely disposed terminal plates 19 aremounted in the casing at opposite sides, each having two terminal screws21 for connecting wires to the plate which are accessible at theexterior through side openings in the casing. The mounting yoke 17 isformed from sheet steel and is provided with the usual mounting tab 23at each end having an opening 25 therein for attaching the receptacle toan outlet box (not shown).

Each terminal plate 19 has integrally formed contact fingers 27 and 29for engaging contact prongs 31 on a plug 33 (FIG. 5) which are insertedthrough slots 35 (FIGS. 1 and 4) in the cover 13.

A grounding contact 37 is disposed adjacent each set of contact fingers27 and 29. The grounding contacts 37 are made from round wire ofresilient high conductivity material, such as bronze, in the generalshape of a harpin. At one end the grounding contact 37 is formed into aring 39 and the two legs 41 at the other end are spaced apart to formcontact portions or fingers 43. The yoke 17 has an opening directlybeneath the contact fingers 43 for receiving the grounding contact 51 ofthe plug 33. The ring portions 39 of the grounding contacts surround thescrews 15 and are electrically connected to the yoke 17, as by welding.Between the ring 39 and 3,036,285 Patented May 22, 1962 the contactportion 43 the legs 41 of the grounding contact are in close proximityto each other, and adjacent the contact fingers .2729 lie in a channel45 (FIG. 4) molded in the cover 13 so as to insulate the groundingcontact from the electrical contacts 27-29. A rib 4'7 molded in the base11 opposite the channel 45 insulates the contact fingers 27 and 29 onopposite sides of the base from each other.

The contact fingers 43 of the grounding contact 37 adjacent the left end(FIG. 2) of the device straddle a central raised portion 49 of the yoketo maintain the contact fingers 43 the proper distance apart to properlyreceive a grounding prong 51 on the plug 33 (FIG. 5). The contactfingers 43 on the right-hand end of the yoke 17 may be disposed in holesin the upwardly directed end portion of the yoke 17 for the samepurpose.

The plug 35 is inserted into the receptacle by first inserting thegrounding prong 51 in an opening 55 (FIGS. 1 and 3) in the cover 13 andthen inserting the male prongs 31 into the slots 35. As the plug 35 isinserted, the grounding prong 51 engages and makes contact with thegrounding contact 37 before the polarized prongs 31 engage the contactfingers 27--29. 'Iihe grounding prong 51 is generally U-shaped and wheninserted into the receptacle made a four-point grounding contact, twopoints of contact being made with the grounding contact fingers '43 asindicated at 57, and two points of contact are made at 59 with the yoke17. This is due to the spring wedging action of the two spring contactfingers 43 on the grounding prong 51 at the points 57 which presses thegrounding prong 51 against the edge 59 of the yoke 17. This assures goodgrounding contact.

The yoke 17, to which the grounding contacts 37 are secured, is providedat one end with integral portions 61 (FIGS. 1 and 2) extending laterallyof the receptacle and having downwardly formed terminals 63 providedwith terminal screws 65 to which grounding wires (not shown) may beconnected to ground the device.

When the plug 35 is removed from the receptacle, the

polarized male prongs 31 first break contact with the contact fingers27-29. Thereafter, the grounding prong 51 breaks the grounding contactthereby maintaining the appliance grounded until after it isdeenergized.

The invention provides an improved grounding contact arrangement for aplug-in electrical outlet receptacle that is simple and inexpensive tomanufacture which provides a superior four-point contact. The device iseasy to make and handle thus reducing the cost of manufacture andassembly.

While the invention has been disclosed in accordance with the provisionsof the patent statutes, it is to be understood that various changes andmodifications may be made in the structural details thereof withoutdeparting from the spirit of the invention.

I claim as my invention:

1. In an electrical wiring device constructed to receive a groundingprong and having a conductive mounting member that can be connected toground potential, a grounding contact being secured to said mountingmember and having resilient arms extending along the mounting member,the extremities of said arms having at least a portion thereof beingangular to said extending direction and in the plane of said arms andbeing spaced from but biased toward each other and being positionedabove an opening in said mounting member and in the entry path of saidgrounding prong, said arm extremities clamping against said groundingprong when the latter is inserted therebetween and said angular armportion effecting an imposition of iorces in said extending directionagainst said grounding prong to urge said grounding prong against amounting member portion adjacent said mounther at multiple points ofcontact.

3 ing member opening whereby said prong is grounded to said mountingmember at multiple points of contact.

2. In an electrical wiring device constructed to receive a groundingprong and having a conductive mounting member that can be connectedltoground potential, a

grounding contact being formed from resilient wire and being secured tosaid mounting member and having arms extending along the mountingmember, the "extremities of said arms having at least a portion thereofbeing angular to the extending direction and in the plane of said armsand being spaced from but biased toward each other and being positionedabove an opening in said mounting member and in the entry path of saidgrounding prong, said arm extremities clamping against said groundingprong when the latter is inserted therebetween and said angular armportion effecting an imposition of forces in said extending directionagainst said grounding prong to urge said grounding prong against amounting member portion adjacent said mounting member opening wherebysaid prong is grounded to said mounting mem- 3.-A' wiring device forreceiving a male connector having current carrying blades and agrounding prong, said Wiring device comprising an insulating base havinga channel for receiving said grounding prong, contact means engagingsaid base for energizing said current carrying blades of said connector,elongated conductive member engaging said insulating base tobe'electrically free of said contact means and being dispose cToutwardly of a reference volume in said base channel, said reference volumebeing defined by said grounding prong when the latter is fully insertedin said base channel,

a resilient grounding contact member being secured to .said conductivemember and having spring arms extending along said conductive memberinto said base channel,

said spring arms being spaced relative to each other said base channeland extending substantially laterally of said base channel, said springarms being biased toward each other so that when said grounding prong isinserted in said base channel said grounding prong can be engaged bysaid spring to form an electrically conductive paththerewith, meansforming a part of said ing said conductive member.

4. A wiring device for receiving a male connector having currentcarrying blades and a grounding prong, said w-in'ng device comprising aninsulating base having a channel for receiving said grounding prong,contact means engaging said base for energizing said current carryingblades of said connector, an elongated conductive member engaging saidinsulating base to be electrically free of said contact means and beingdisposed outwardly of a reference volume in said base channel, saidreference volume being defined by said grounding prong when the latteris fully inserted in said base channel, a resilient grounding contactmember being secured to said conductive member and having spring armsextending along said conductive member into said base channel, saidspring arms being spaced relative to each other in said base channel andextending substantially laterally of said base channel, said spring armsbeing biased toward each other so that when said grounding prong isinserted in said basechannel said' grounding prong can be engaged bysaid spring arms to form an electrically conductive path therewith,means forming a part of said spring arms for urging said grounding prongin the extending direction of said spring arms against a portion of saidconductive member adjacent said reference volume in said base channel,said conductive member portion extending into a reference plane throughsaid spring arms and being laterally and resiliently engaged with said'spn'ng'arms prior to insertion of said grounding prong,

and means for electrically grounding said conductive member.

References Cited in the file of this patent UNITED STATES PATENTS

